* [fix] implementation fault on avl

* [fix] mm may free varea allocated statically

* [test] add test and benchmark for avl

fix bugs on cache maintenance when starting user app

* [rt-smart/mem] remove pv_offset

* [rt-smart] list kernel space command

* [rt-smart] restore ioremap region

* [revert] restore kernel space isolation

* [rt-smart/pv_off] code format

* [rt-smart] add get_pvoff()

* [pvoffset] pvoff as constant for C codes

* [pvoff] pvoff as interfaces

* [rt-smart] asid for c906

* [rv64/bsp] porting to mm

* [mm] report more info for debugging

* [fix] code format

* [libcpu/c906] porting to RTOS

* [fix] using rtdbg api

* [fix] add return

* [fix] report more information for debugging

* [fix] use assert 0 for unrecoverable error

* [mm] enable mm on armv7, armv8, rv64 only

* [mm] config on ARCH_MM_MMU

synchronize virtual memory system works.
adding kernel virtual memory management layer for page-based MMU enabled architecture
porting libcpu MMU codes
porting lwp memory related codes